Merge session format migration into live assistant stream

apps/web/tests/scaffold.ts

@@ -812,7 +812,7 @@ function rawSessionLog(session: Session): string {
       ...header.parentSession === undefined ? {} : { parentSession: header.parentSession },
       ...header.isSeeded ? { seedLength: Number(session.inheritedEventCount) } : {},
       ...header.origin === undefined ? {} : { origin: header.origin },
-      ...header.delegationDepth === undefined ? {} : { delegationDepth: header.delegationDepth },
+      delegationDepth: header.delegationDepth ?? 0,
       ...header.agentPreset === undefined ? {} : { agentPreset: header.agentPreset },
     }),
     ...packChunkRuns(session.snapshotEvents()).map(record => JSON.stringify(record)),

packages/experimental/webworker-runtime/tests/fixtures/vfs-example/home/storages/session_projcache.json

@@ -1,7 +1,7 @@
 {
   "unit": {
     "name": "session_projcache",
-    "version": 6
+    "version": 7
   },
   "global": null,
   "tables": {

packages/experimental/webworker-runtime/tests/vfs-example-fixture.spec.ts

@@ -74,7 +74,7 @@ describe('WebWorker preview VFS example', () => {
         }>
       }
     }
-    expect(cache.unit).toEqual({ name: 'session_projcache', version: 6 })
+    expect(cache.unit).toEqual({ name: 'session_projcache', version: 7 })
     expect(cache.tables.sessions[VFS_EXAMPLE_SESSION_IDS.main]).toMatchObject({
       identity: {
         formatVersion: SESSION_FORMAT_VERSION,